Some chemicals, e.g., liquid organic chemicals, although they are useful, are also hazardous to humans and other life forms. As a result, they must be specially handled during process, storage and transportation. Suitable handling provisions are designed by taking a range of the properties of the hazardous chemicals, measuring the extent of each, determining the hazard associated with each, and then correlating these properties with the technology available for appropriate hazard control. Properly equipped vessels can adequately process, transport and store such hazardous chemicals. Linings, for example, are used to protect the product from contamination and protect the vessel from attack by the product or from leakage via the porosity of the vessel material.
In the event of damage or extensive wear, these vessels must be taken out of service until refurbished or they must be condemned for disposal. Condemnation occurs because of a worn out vessel body, fittings, insulation or structures to which these vessels are permanently or semipermanently attached, and more especially because of damaged linings. Also, physical damage may occur to the vessel or its structure such as by expansion, contraction, weather, motion, momentum, accidental impact and the like such that the vessel must be taken out of service.
Even after the vessel is taken out of service, irrespective of whether it will be condemned or refurbished, it must be decontaminated before it can be freely handled or disposed of. Most often the larger vessels are decontaminated and cup up for salvage of their metal value.
The present invention relates to a method of decontaminating vessels containing minor contaminating amounts of oxidizable liquid organic chemicals. More particularly, it relates to a method of decontaminating large vessels used for storing, transporting, or processing oxidizable liquid organic chemicals such as, for example, railroad tank cars, storage and process vessels, and portable tanks containing alkyl lead compounds, e.g., tetraalkyl lead compounds.
One way in which vessels can be decontaminated of oxidizable liquid organic chemicals is by chemical cleaning with an oxidizing agent. This method, however, is not always completely satisfactory because, as a result of, for example, a damaged lining, the contaminating chemical is typically absorbed deep in the vessel walls where the oxidizing agent cannot reach. Therefore, even after chemical cleaning, the deeply embedded residue eventually diffuses to the metal surface, thereby posing a future hazard. moreover, unless the oxidizing agent can effectively attack the vessel liner, this must also be removed. In addition, the spent oxidizing agent itself may pose environmental hazards; hence provisions must be made for safely disposing of this spent material.
The most effective method of decontamination is to heat the vessel to a high temperature for a given period of time in order to decompose the oxidizable liquid organic contaminant into combustion gases and/or solid inorganic metal oxides in the case where the contaminant contains a heavy metal. In the past, this heating has been accomplished by placing the entire vessel in an annealing furnace, i.e., a large chamber with natural gas burners placed around the periphery of the chamber. However, this mode of decontamination is unsatisfactory. Firstly, this method is not fuel efficient because the annealing furnace uses an excess of fuel to heat the empty space around the vessel to be decontaminated. In order to decontaminate the vessel effectively, the inside walls of the vessel should receive the maximum exposure to the heat. Such result is not obtained by directing the heat at the outside walls. Secondly, the combustion gases from the heating operation can contain solid contaminant by-products as well as particulates from the oxidized lining of the vessel, which must be filtered, and annealing furnaces are not equipped with the necessary filters.